Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 261125

Area Forecast Discussion
National Weather Service Sioux Falls SD
625 AM CDT Tue Sep 26 2017

.SHORT TERM...(Today and Tonight)
Issued at 405 AM CDT Tue Sep 26 2017

The end is in sight, at least with regards to the precipitation
which has been slow to move across the region over the past few
days. Deeper drying apparent on IR/water vapor satellite just
pushing into the southwest corner of the CWA as of 08Z. This should
continue to progress eastward through the morning, and accompanying
subsidence should push our lingering light rain/drizzle east of the
forecast area by mid morning. Stratus looks to remain a bit more
persistent, but continued subsident flow and deeper drying should
aid in breaking up the low clouds from southwest to northeast
through the afternoon. Weak cool advection will keep temperatures
below normal despite the late day sunshine, with highs in the upper
50s-mid 60s expected.

Anticipate mostly clear skies by mid evening, with light winds in
surface ridge allowing temperatures to drop off into mainly lower
40s most areas overnight. With recent rains, and limited mixing of
the near surface moisture through today, may have to watch for areas
of fog developing overnight. However, potential looks to be shallow
and brief based on forecast soundings, so did not include a mention
at this time.

.LONG TERM...(Wednesday through Monday)
Issued at 405 AM CDT Tue Sep 26 2017

The broad upper trough which has plagued us through this past
weekend slides eastward through the Great Lakes mid-late week, while
a ridge builds over the western CONUS. Should see some moderation in
temperatures Wednesday and Thursday, with highs mid 60s-mid 70s.
Models still show a weak wave/associated cool front dropping south
through the Upper Midwest Thursday night, though most generally a
little weaker with the feature than previously seen. The front will
knock temperatures back a few degrees for Friday, mainly in eastern
areas, but not expecting any precipitation as stronger forcing will
remain to our east.

Next weekend sees an upper ridge move quickly eastward across the
region Saturday, followed by another trough swinging through the
Rockies into early next week. not a great deal of agreement between
the models in handling of this trough, with some quickly ejecting
the trough northeastward into central Canada by late Monday, while
others lag the trough back over the western Dakotas. System should
bring some increased rain chances back to the region, possibly as
early as Saturday in parts of the west, but with the greater chance
by later Sunday/Sunday night. The more progressive solutions bring
drier conditions for Monday, while the slower lingers a decent
threat of rain into the work week. Given the model differences, did
not alter consensus pops/temperatures in the longer range of the
forecast. In any case, appears to be enough instability ahead of the
wave/surface boundary for a mention of thunder Sunday into Monday.
As far as temperatures, timing differences again come into play, but
generally looking for readings favoring the warm side of normal as
we transition into October early next week.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 618 AM CDT Tue Sep 26 2017

MVFR/IFR stratus will erode west to east through the day today,
with the deck finally clearing out of FSD and SUX by around 21z.
Winds will be out of the northwest for much of the TAF period.
With light winds and a good amount of surface moisture thanks to
the recent rainfall, would not be surprised to see some patchy fog
Tuesday night. Have not put any visibility reductions in the TAFs
at this time, but did add lines with light and variable winds to
hint at the fog potential.




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